Chap 2 - Combustion Systems Flashcards
Components of a basic combustion chamber
Flame tube
Outer air Casing
Flame tube
Withsatmds very high pressure
Nimonic alloy
NO PEAK PRESSURES
Holes around circumstance for combustion and cooling
Outer Casing
Subjected to lower temperatures
Alloy steel
Overheating will show - discolouration
What percentage of air goes through the combustion chamber
18-25%
What is the dilution zone used for
Cool the hot gases to a acceptable temperature
What is the primary zone
Air enters combustion chamber through swirl vanes and mixs with atomizer fuel from burner nozzle or flare stabilises the flame by creating slow moving zone of air
What is the air/fuel ratio in combustion chamber
60:1
Two main combustion chambers
Annular
Reverse flow
Annular chamber
Circular flame tube which allows the compressor shaft to go through the center
Adv of annular combustion
Good utilisation of area
Structural part of engine
Annular gas flow
High efficency
Large total combustion area
Reverse flow combustion chamber
Has been shortened in overall length
Looks like a U shape
Good for helicopters
Cushion chamber drains
A.D.V how’s it used
Use an automatic drain valve
Combustion chamber pressure falls off the spring will open the drain
Fuel nozzles (burners)
Introduce fuel into the combustion chamber
Two types of fuel nozzles
Atomizer and vaporisers
Three the types of atomizers
Duplex
Rotary
airspray nozzle
Duplex atomizer
Two independent orifices
Smaller one operates lower flows
Bigger one operates higher flows
Both can be used when pressure and fuel flow is high
Rotary atomizer
Centrifugal motion will eject the fuel
airspray nozzle (looks like a golf tee)
Mixes primary combustion with injected fuel
Reduction in carbon and exhaust smoke
Low pressures required to atomize the fuel
Vaporiser
sprayed from feed tubes into vaporising tube.
Tubes are heated by combustion and fuel is therefore vaporised before passi g intot the flame tube
Adv of vaporisers
Produce less smoke
Flame can be stabilised
Combustion zone is shorter
Filters are used to protect the burner from debris
